TARGETING AND SELECTIVE RETENTION Targeting EVs to specific cell types could indeed be considered a holy grail of EV therapeutics, since cell specificity reduces the necessary dose and minimizes off-target effects. EV mimetics from natural sources will be different from native EVs to the extent that specific biogenesis pathways impress characteristics on EVs. Considering that the surface of a 100 nm diameter EV would be 1/250,000 of the surface of a 10 micron diameter cell, the limited surface of an EV would be able to accommodate at a maximum only a few dozen of the most abundant surface marker such as tetraspanins, in comparison with millions of copies in a single cell. EVs cannot truly "home" to a specific cell, and researchers will likely need to focus on selective retention of EVs by the target cell while also considering plausible strategies for blocking non-specific uptake of EVs by off-target cells. [Extracted from the article]